F100 Throttle Position Sensor

[almetelo]

Hi!

Checked the values (Volts) of TPS on my 2004 F100 (carbs) and found that following results:
TPS input 4.20V
TPS output 0.7V

The service manual recomends the following values:

TPS input 5V +/- 0.25V
TPS output 0.7V +/- 0.02V

Tryed to tune it for the reference values but with no sucess
When increase volts on input TPS decrease on output TPS and vice versa

Which TPS IN or OUT should I choose to tune right? or this is not critical?

[boscoe99]

You can't tune it for input voltage. Input voltage is what the CDI feeds to the TPS.

You might want to check the electrical connections between the CDI and the TPS to make sure they are clean. Any corrosion build up on terminal pins and/or sockets may result in a voltage drop.

Make sure that good battery voltage (~12.7 volts) is being supplied to the ECU and that the grounds are clean and tight.

What problem are you having? If the have the correct output voltage then even if the input voltage from the CDI to the TPS is slightly below specifications it might not cause a running issue.

Let's hope the CDI is not failing.

[rodbolt17]

and remember.
engine MUST be running to test or adjust.
its a self learning thing.

[almetelo]

Hi Boscoe and Rod!

Thanks for replay!

Everything is OK, I just have been adjusting the throttle level and shift cable according the service manual because the carburetor pickup timing was not good.
Then decide to check the TPS values (I know the TPS shoundnt interfer with throttle control)I did it just to make sure was all OK.

Then found the above results and tryed to tune it...
If I cant tune the input voltage of TPS why the volts increase or decrease when I slide it?
Other thing was that when tryed to increase the TPS to 5v (or when I was monitoring the TPS IN) the idle speed (RPM) also increaded a little.

Battery is good, just 3 months old.

Yes, manual recomends to warm up 1st then do the test and with motor stopped got no readings.

I may not have an issue, motor is working fine, just want to hear you... I thought I could do something to leave it on the reference values

Thanks!

[rodbolt17]

either your confused on reading the manual or its not a factory Yamaha manual.
the F100 at key on engine off has NO voltage to the 5v ref line at the TPS.
only when the engine is running.
that's why the tune up spec guide gives the values with a note"engine must be running".

only thing the TPS does on that model is alter base ign timing.
base timing is fixed due to the relationship of the stator plate and the flywheel .
toss the TPS in the creek and the engine will run.
idle speed will increase and top speed cannot be reached and ign timing will be fixed at about 10* BTDC at all RPM's.

but it is self learning and will compensate for a varying input ref V.

[boscoe99]

Hi Boscoe and Rod!

Thanks for replay!

Everything is OK, I just have been adjusting the throttle level and shift cable according the service manual because the carburetor pickup timing was not good.
Then decide to check the TPS values (I know the TPS shoundnt interfer with throttle control)I did it just to make sure was all OK.

Then found the above results and tryed to tune it...
If I cant tune the input voltage of TPS why the volts increase or decrease when I slide it?Other thing was that when tryed to increase the TPS to 5v (or when I was monitoring the TPS IN) the idle speed (RPM) also increaded a little.

Battery is good, just 3 months old.

Yes, manual recomends to warm up 1st then do the test and with motor stopped got no readings.
I may not have an issue, motor is working fine, just want to hear you... I thought I could do something to leave it on the reference values

Thanks!

The TPS is a potentiometer. A variable resistor of sorts. It can only provide an output voltage that is equal to or below the input voltage.

Potentiometer - Wikipedia, the free encyclopedia

With a five volt input and no resistance from the potentiometer the output will be five volts. With a five volt input and some amount of resistance the voltage will decrease. As the variable resistor adds or takes away resistance the voltage decreases or increases. The CDI sees a voltage and interprets it as the throttle opening position. Based on throttle opening position the CDI does whatever it has been programmed to do.

The Yam SM and tune up specs say to test input voltage with the motor idling. Some (most) motors will provide an input voltage with jus the key turned on, but not the F100 carbureted model.

[almetelo]

Yes, manual is original.
Maybe didnīt explaine myself very well. I did it as you mention, like is on manual.
Later will post that page, canīt do it from the phone.

Thanks for be more specific and explain what TPS does.

Will leave it like it was (and still is because left it the same way it was)

[almetelo]

Thats the page of SM I guided for...

[boscoe99]

Thats the page of SM I guided for...

Note that the page says the engine is to be idling when checking the voltage from the CDI to the TPS.

Would be nice if Yamaha explained that there is no output voltage when the motor is off, but like I said their data is marginal at best.

Remember, if it ain't broke don't go fixin' it!

[almetelo]

Remember, if it ain't broke don't go fixin' it!

Thats a good point and I agree but sometimes you (me) canīt learn only reading...

Lets clear what wrote...

"Yes, manual recomends to warm up 1st then do the test and with motor stopped got no readings"

What I mean:

1st - Yes, manual recomends to warm up 1st then do the test
2nd - with motor stopped got no readings (I checked the TPS anyway, wouldnt wurt)

Thats because of my bad English - Sorry, I'm trying to improve.

[boscoe99]

[madharchod]

just take the TPS out and check for the continuity with the multimeter if there is one present its stuffed ,if there is resistance then you might have to do the adjusting while running the motor as the ECU is responsible for the rest,it should should self adjust while running unless your carbs are playing up,
another thing you can check is your wiring for corrosion as sometimes they bring this along too